import java.util.*;
public class AaddBtimeC
{
	public static void main(String[] args)
	{
		long a,b,c;
		Scanner s=new Scanner(System.in);
		a=s.nextLong();
		b=s.nextLong();
		c=s.nextLong();
		System.out.print((a+b)*c);
	}
}